#include <stdio.h>
#include <math.h>

long n,i,j,k,p,x,d,a[2000];

int main(){


	FILE *fin = fopen("ciur.in", "r");
	FILE *fout = fopen("ciur.out", "w");
	fscanf(fin,"%ld", &n);


	for (i=2;i<=n;i++){
		d=2;
		p=1;
		for(j=d;j<=sqrt(i);j=j+d){
			if (i%j==0)
				p=0;
			d=d+1;
		}

		if (!(p==1))
			a[i]=1;
	}
	for (i=2;i<=n;i++){
		if (a[i]==0)
			x=x+1;
	}




	fprintf(fout,"%ld", x);
	fclose(fin);
	fclose(fout);



   return 0;
}